This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. My laboratory is interested in structural aspects of cell-surface receptor/ligand interactions with relevance to human health and disease. Through structural analysis we hope to answer basic mechanistic questions about transmembrane signaling, as well as produce structural data that can be used as a template for drug design. We are engaged in expression and crystallization studies of numerous glycoprotein receptors both alone and in complex with their ligands. We are expressing both soluble receptor domains as well as full-length integral membrane proteins. The receptor systems we study are primarily in the immune and nervous systems, with a special emphasis on understanding cross-reactivity in molecular recognition. Most of our projects we are critically dependent on the ability to collect x-ray data at a synchrotron facility due to the generally small and moderate quality of the crystals which we can grow of large and hetero-geneous protein complexes.